Edwards, MarkNishida, Shin'ya2015-12-132015-12-130042-6989http://hdl.handle.net/1885/77958Motion perception appears to be mediated by, at least, two systems: a first-order and a second-order system. To investigate the degree of interaction between these systems, we used a contrast-reversing global-motion stimulus in which the signal dots reverse their contrast polarity as they move. In response to such a stimulus, fullwave-rectifying second-order units would signal motion in the displacement direction and first-order units would signal motion in the opposite direction (reverse-phi motion). If these signals were of equal strength, then any inhibitory interaction between them would lead to motion nulling. Such a situation would account for the failure to perceive coherent motion with such a stimulus in a previous study [Vis. Res. 34 (1994) 2849]. In order to test for this possibility we manipulated the stimulus in order to reduce the strength of the second-order response relative to the first-order response. This was achieved by: decreasing dot contrast; increasing stimulus eccentricity; and increasing dot speed. These manipulations resulted in an increase in the perception of (first-order mediated) reverse-phi motion. We conclude that interaction between first- and second-order motion signals occur at the local-motion-pooling level.Keywords: article; brain cortex; color; contrast; controlled study; human; human experiment; luminance; motion; normal human; perception; priority journal; signal transduction; visual stimulation; Adaptation, Ocular; Contrast Sensitivity; Humans; Motion Perception;200410.1016/j.visres.2004.03.0162015-12-11